The percentage of overweight Americans has increased in recent decades. Despite many possible reasons for the increase in obesity cases, the root cause is essentially a greater overall energy intake than energy expenditure.

One reason for obesity prevalence in the U.S. may be larger food portion sizes, especially outside of the home, which encourage individuals to eat more calories.

Portion sizes for popular take-out restaurants, fast-food chains, and family restaurants were measured and compared to U.S. Department of Agriculture (USDA) and Food and Drug Administration (FDA) standards, and to portion sizes in the past. Information was obtained from portion weights, package labels, and manufacturer claims. Below are the findings of the study, which appeared in the American Journal of Public Health: